Sevoflurane inhalational anesthetic has got pulmonary effects such as bronchodilatation. These effects could be of interest in intensive care patients ventilated in pressure support ventilation mode. The purpose of this study is to evaluate mechanical respiratory effects of sevoflurane administered through a new specific heat and moister exchanger called the Anesthetic Conserving Device (AnaConDa®) in pressure support ventilation in intensive care patients. In fact, dead space and resistance generated by the device could cancel and even deteriorate the potential positive effects of sevoflurane on ventilation.